How Do You Know if a UTI Has Spread to Your Kidneys?

  • Medical Reviewer: Dany Paul Baby, MD
Medically Reviewed on 6/29/2022

What is a UTI?

A UTI is an infection anywhere in the urinary tract. Signs that a UTI has spread to the kidneys include chills, high fever, nausea, and vomiting, and other signs.
A UTI is an infection anywhere in the urinary tract. Signs that a UTI has spread to the kidneys include chills, high fever, nausea, and vomiting, and other signs.

The urinary tract consists of two kidneys, two ureters that carry urine from the kidneys, the urinary bladder, which receives urine from the ureters, and the urethra, from which urine exits the body. When we speak of a UTI, we generally mean a urinary bladder infection. Can a UTI become a kidney infection
That's an important concern since kidney infections are dangerous. The kidneys remove wastes from the body, maintain the balance of water and crucial electrolytes like sodium and potassium, and have many other functions. 

Normally, urine is sterile. The kidneys, ureters, urinary bladder, and urethra have no bacteria or other germs. A UTI is an infection of any part of the urinary system. Urinary infections are common, and more than half of all women will have at least one in their lives.

Most infections of the urinary tract are ascending infections. The bacteria enter from the urethra and travel up to the bladder. Infection of the bladder is called cystitis. UTI is four times as common in women as in men since women have a shorter urethra.

A UTI is an infection anywhere in the urinary tract. Bladder infections are the most common and are called cystitis. Infections that only involve the urethra are called urethritis. A kidney infection, called pyelonephritis, is also a type of UTI.

The symptoms of cystitis

The usual symptoms of an infection of the urinary bladder:

  • Burning or pain when passing urine
  • A need to pass urine again and again, with very little urine passed
  • Pressure or pain in your lower belly
  • Urine that looks cloudy or reddish
  • Urine with a bad smell
  • Tiredness and feeling unwell, perhaps a low fever

How do your kidneys get infected?

Normally, an infection in the bladder can't reach the kidneys because the urinary tract has a one-way flow. Urine flows from the kidneys to the bladder and then out of the body. Any bacteria in the urinary tract are flushed out.

Kidney infections happen when bacteria travel upwards from the bladder and reach the kidneys. This usually only occurs when you have a condition called vesico ureteric reflux (VUR). Urine flows back from the bladder into one or both ureters, usually when you pass urine. 

Kidney infection can also happen when bacteria in the blood reach the kidneys and start an infection (hematogenous UTI). This situation is rare in adults and usually follows surgery.

Signs that your kidneys are infected

Kidney infections are a type of UTI, but the symptoms differ somewhat from those of a bladder infection. Symptoms of kidney infections include:

When a UTI spreads to the kidneys, the symptoms are severe. The fever is often very high, and you may feel very sick. People over 65 may have different symptoms — confusion, hallucinations, or garbled speech. They may wet themselves more than usual and experience shivering or shaking.

How is a kidney infection diagnosed?

If you have any symptoms of a UTI, you should visit your doctor. They will ask you to pass urine into a cup for testing. The laboratory will examine your urine chemically and under a microscope. UTI causes pus cells and blood in your urine. Large amounts of blood are more likely in cystitis than in kidney infection. White blood cell casts are a sign of kidney infection.

A sterile container is used for collecting urine for culture. This test takes three to five days and tells your doctor what bacteria are causing an infection. The report also indicates what medicines are likely to be effective. If you are not better after the initial treatment, the culture results will guide further treatment.

Your physician may ask for special tests, including blood tests for infection and kidney function. Sometimes doctors call for ultrasound, CT or MRI scans, or for scans made after contrast media injections to judge kidney function.

Is a kidney infection an emergency?

Yes. A kidney infection is bad news. Kidneys are essential organs and can be rapidly damaged by bacteria. Without prompt treatment, the kidneys can be permanently damaged. 

Kidney infections (pyelonephritis) can cause high blood pressure and kidney failure. The infection also leads to scarring in the kidneys. Scars can progress to chronic kidney disease and later to renal failure. Renal failure has to be treated by repeated dialysis or a kidney transplant. It is crucial to diagnose and treat kidney infections quickly.


How much urine does the average adult pass each day? See Answer

Treatment of UTI 

When you have symptoms that suggest a UTI, your physician will first order some tests. They probably won't wait for the results — they'll start treatment right away.

The most important part of treatment is an antibiotic. Since infections can cause permanent damage, your physician will prescribe an antibiotic as soon as you have given your urine sample to the laboratory. You'll have to take the antibiotic for several days. Completing the course is vital for a cure. Some antibiotics have to be given by injection or in an intravenous infusion. You may need to be admitted to a hospital for such treatment.

If you are well after completing the treatment, your physician won't ask for any testing. But they may advise repeat testing if you have symptoms again within a few days of completing the treatment.

If you have kidney infections frequently, your doctor may prescribe a low dose of an antibiotic to be taken every night. They might also ask you to take a dose after sex.

Preventing UTIs

Urinary tract infections are common, but they can become serious if they reach the kidneys. To prevent UTIs:

  • Pass urine frequently. Don't hold urine for more than 3 to 4 hours. 
  • Try to urinate before and after sex.
  • After using the toilet, wipe your genital area from front to back. This prevents bacteria from the anal area reaching the urethra.
  • Drink 6 to 8 glasses of water and other liquids a day.
  • Showers are best. Limit baths to 30 minutes or less.
  • Change out of wet or damp bathing suits or gym clothes quickly.

What you shouldn't do:

  • Don't avoid passing urine when you feel the urge.
  • Don't hurry — take your time and fully empty your bladder.
  • Avoid scented soap and vaginal douches.
  • Avoid sugary food and alcoholic drinks.
  • Don't use female condoms or diaphragms with spermicidal cream. 


Your kidneys are essential organs that can be damaged by infections. If you have a UTI, watch out for signs that it has spread to your kidneys. Such infections can cause permanent kidney damage. Early and complete treatment prevents a UTI from becoming a kidney infection.


Urinary Incontinence in Women: Types, Causes, and Treatments for Bladder Control See Slideshow

Health Solutions From Our Sponsors

Medically Reviewed on 6/29/2022

American Academy of Family Physicians: "Urinary Tract Infection."

American Family Physician: "Diagnosis and Treatment of Acute Pyelonephritis in Women."

National Health Service: "Urinary tract infections (UTIs)."

National Institutes of Diabetes and Digestive and Kidney Diseases: "Definition & Facts of Kidney Infection (Pyelonephritis)."

National Institutes of Diabetes and Digestive and Kidney Diseases: "Symptoms & Causes of Kidney Infection (Pyelonephritis)."

National Institutes of Diabetes and Digestive and Kidney Diseases: "Treatment for Kidney Infection (Pyelonephritis)."

National Institutes of Health: "Bladder Infection (Urinary Tract Infection—UTI) in Adults."

National Library of Medicine: "Urinary Tract Infections."

US Department of Health and Human Services: "Urinary Tract Infections."